Drying Stress Relaxation of Wood Subjected to Microwave Radiation

He, Qiaojun; Wang, Ximing

doi:10.15376/biores.10.3.4441-4452

Cited by 3 publications

(4 citation statements)

References 9 publications

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“…When drying wood, microwave conditioning improves the drying performance of 25 mm thick wood of Eucalyptus urophylla and Eucalyptus tereticornis. As we extend the duration of the microwave radiation, the reduction in drying stress increases [13]. The impact of various MW intensities on the permeability of Eucalyptus and Radiate pine wood was investigated by Vinden P, et al [38] and found that radiation penetration depth is infl uenced by the material's dielectric properties.…”

Section: Impact Of Microwave Treatment On Strength Propertiesmentioning

confidence: 99%

“…Due to its strong polarity, water absorbs microwave energy more effi ciently than wood. As a result, areas with higher moisture content experience higher temperatures [13]. When Vermaas HF [14] investigated the mechanism, he reported that the frequency, voltage, and two characteristics of the wood's substance all aff ected how hot the material became.…”

Section: Dielectric Heatingmentioning

confidence: 99%

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Effect of Microwave Treatment on Strength and Permeability of Wood: A Snapshot Review

Sharma,

Kumar

2023

J Biomed Res Environ Sci

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Microwave treatment is a promising technique for modifying the properties of wood. It has gained popularity as an alternative method to conventional treatments for improving the properties of wood. Microwave drying has shown that it reduces the drying stresses and improve the quality of wood compared to traditional drying methods. This efficient heating reduces the risk of deformation, cracking, and other defects that can occur with prolonged exposure to high temperatures during traditional drying and also helps in increasing the permeability of wood. This snapshot review provides an overview of the effect of microwave treatment on the strength properties and permeability of wood with variations in parameters such as the frequency, power, and treatment time along with the potential benefits and drawbacks of this method. Overall, the review indicate that microwave treatment is an effective method for modifying the properties of wood and has the potential to improve its performance in various applications.

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Section: Impact Of Microwave Treatment On Strength Propertiesmentioning

confidence: 99%

Section: Dielectric Heatingmentioning

confidence: 99%

Effect of Microwave Treatment on Strength and Permeability of Wood: A Snapshot Review

Sharma,

Kumar

2023

J Biomed Res Environ Sci

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“…However, low-density woods seem favorable to drying, apparently because of their ability to deform internally to relieve the shrinkage stress. Shrinkage stress during drying can be relieved by several methods such as: (1) by increasing the surface moisture content (MC) of the wood via steam conditioning (Keey et al 2000); (2) by decreasing the internal MC of the wood; and (3) by increasing the MC of external wood and by decreasing the MC of internal wood simultaneously using microwave conditioning (Grinchik et al 2015;He and Wang 2015). Figure 5 shows that the length of surface checks increased linearly with increased treatment temperature both in sapwood and heartwood.…”

Section: Surface Checksmentioning

confidence: 99%

Effect of mechanical restraint on drying defects reduction in heat-treated okan wood

Hidayat

Jang

et al. 2017

BioRes

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Mechanical restraint through the use of clamps was applied as an attempt to prevent drying defects during the heat treatment of high-density wood. Boards of okan (Cylicodiscus gabunensis (Taub.) Harms) with the initial moisture content of 8.99% and 9.68% for sapwood and heartwood, respectively, were prepared. The boards were heat-treated under an oxygen atmosphere at the peak temperatures of 160 °C, 180 °C, 200 °C, and 220 °C with a residence time of 2 h. The occurrence of drying defects as checks (i.e., surface and end checks) and warps (i.e., bow, cup, and twist) were evaluated. Heat treatment stimulated the occurrence of drying defects in okan wood. The results revealed that the surface checks, end checks, and twists increased linearly with increased temperature. The occurrence of warps, such as bow and cup, after heat treatment was relatively low. Heartwood showed a higher degree of drying defects compared to the sapwood. Application of mechanical restraint by clamping efficiently decreased the occurrence of drying defects of okan wood, particularly surface checks, end checks, and twists.

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“…Their experiments were based on previously developed simulation models, and they conclude that the three options provide similar results for radiata pine. More recently, He and Wang (2015) studied the moisture equalization of sawn timber, which does not necessarily mean stress relief, and they posted three different ways theoretically possible to equalize the moisture distribution in timber: by increasing the MC of the surface, by reducing the MC of the core, or by a combination of these methods. They state that reducing the MC of the core without modifying the MC of the outer regions is not applicable.…”

Section: Introductionmentioning

confidence: 99%

The conditioning regime in industrial drying of Scots pine sawn timber studied by X-ray computed tomography: a case-study

et al. 2020

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Industrial drying of sawn timber is a process driven by a difference in moisture content (MC) between the core and the surface as moisture moves from the wet inner region towards the drier surface. After drying, the timber surface is always drier than its core, and stresses have developed within the wood volume. If the timber is to be further processed, these stresses and the moisture gradient need to be reduced to avoid unwanted distortion, i.e. the timber needs to be conditioned. Conditioning is usually accomplished by exposing the timber to a hot and humid climate after the drying regime. The conditioning regime is essential for timber quality, and it is energy and time consuming; therefore of interest for optimisation. This research was a case study where for the first time the MC during conditioning was studied in an X-ray computed tomography (CT) scanner. The aim was to test a previously developed algorithm and investigate the influence of MC and heartwood-sapwood proportion on the effectivity of the moisture equalisation in 30 mm thick Scots pine boards. The MC was estimated from CT data acquired during the drying and conditioning of the boards in a lab-scale kiln adapted to a medical CT scanner. Results show that the algorithm can provide relevant data of internal MC distribution of sawn timber at the pixel level. Furthermore, for the drying schedules studied, the conditioning at low MC (8%) does not need to be longer than 3 h, while higher MC (18%) requires a longer conditioning.

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Drying Stress Relaxation of Wood Subjected to Microwave Radiation

Cited by 3 publications

References 9 publications

Effect of Microwave Treatment on Strength and Permeability of Wood: A Snapshot Review

Effect of Microwave Treatment on Strength and Permeability of Wood: A Snapshot Review

Effect of mechanical restraint on drying defects reduction in heat-treated okan wood

The conditioning regime in industrial drying of Scots pine sawn timber studied by X-ray computed tomography: a case-study

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